Continuous hot rolling mill with metal block conveying apparatus

ABSTRACT

A continuous hot rolling mill with a metal block conveying apparatus and a metal block joining apparatus which moves with the metal blocks along the metal block conveying apparatus to conform a joining operation. The metal block conveying apparatus uses rollers supported by cylinders with a common hydraulic circuit which allows the cylinders to follow guide rails on the metal block joining apparatus and lower out of the path of the metal block joining apparatus and then return to a metal block support position after the metal block joining apparatus&#39; passage without individual control circuits and valves for each of the cylinders.

This appln is a Div of Ser. No. 08/946,638 filed Oct. 7,1997 now U.S.Pat. No. 6,164,525, which is a division of Ser. No. 08/387,788 filedFeb. 15, 1995 U.S. Pat. No. 5,753,894 and a continuation ofPCT/JP94/00968 filed Jun. 15, 1994.

TECHNICAL FIELD

The invention relates to a continuous hot rolling method of metal blocksfor butt-joining a preceding metal block and a succeeding metal blockand continuously performing a hot finish rolling, as well as a metalblocks joining apparatus, a table roller conveyor, a poor joined portionremoving apparatus and a metal blocks cooling apparatus which aredirectly used to carry out such method.

BACKGROUND ART

Conventionally, in hot rolling lines of metal blocks comprised, forexample, of steel, aluminum, copper and the like, the metal blocks to berolled are heated, rough rolled and finish rolled one by one, so as tobe finished into a plate having a predetermined thickness. Such arolling system suffers from disadvantages that a poor threading of therolled material in the finish rolling inevitably causes the line tostop, and a poor shape of fore end portion and rear end portion of therolled material results in a low yield.

Therefore, it is a recent trend to carry out an endless rolling in whichthe metal blocks to be rolled are connected at the fore end and rear endportions thereof prior to the finish rolling and continuously conveyedto the hot rolling line. As prior art in this connection, variousproposals are disclosed, for example, in Japanese Patent ApplicationLaid-Open Nos. SHO-58-112601, SHO-60-244401, SHO-61-159285,SHO-61-144203, SHO-62-142082, SHO-62-234679, HEI-4-84609, HEI-4-89120,HEI-5-185109, etc.

According to a general practice, the regions of the metal blocks in thevicinity of their respective end portions are clamped and supported byclamps on the inlet side of the rolling equipment and the to-be-joinedportion is heated to an elevated temperature and pressed and joined byheating means as the endless rolling of the metal blocks is performed.However, in joining the metal blocks which are passed through theabove-mentioned processes, there still remain various disadvantages suchas those described below, in connection with which there have beendemands for improvements.

(2) The joining apparatus for joining the metal blocks is generallyconstructed such that a carriage movable on a conveying line of themetal blocks is provided with clamps for fixing the metal blocks,heating means (e.g., an induction heating coil) for heating the metalblocks to an elevated temperature, and pressing means for pressing theend portions of the metal blocks with each other. In this instance, ithas been a general practice to cause the heating means to approach themetal blocks only in the use condition and maintain it off the lineexcept during the heating, and such a practice proved to be free fromproblems. However, the clamps and the pressing means remain mounted onthe carriage and hence located on the conveying line of the metalblocks, so that they are subjected to a substantial thermal load andtheir lives become relatively short. Moreover, the carriage mounting theclamps and the pressing means cannot be attached with table rollers forstructural reasons, so that scratches are formed due to the slidingmotion of the metal blocks in the carriage when scales are depositedthereon. Further, the maintenance of the clamps and the pressing meanscannot be performed except when the transfer of the metal block isstopped or when the rolling is stopped.

(3) In the rolling line provided with a movable-type joining apparatussuitable for joining the metal blocks during the running, there isrequired an ascending and descending timing control with which the tablerollers supporting the metal blocks are moved vertically correspondingto the running of the joining apparatus. A conventional table rollerdisclosed, for example, in Japanese Patent Application Laid-Open No.HEI-4-367303 lacks in accuracy and reliability as described below. Also,in connection with the driving cylinders for causing the vertical motionof the table rollers, it has been recognized disadvantageous that thehydraulic apparatus has to be large in scale due to a requirement forsubstantial flow rate of operating oil, thereby giving rise tosubstantial increase in the power loss and the running cost.

FIG. 4 shows a construction of the equipment disclosed in theabove-mentioned patent, and FIG. 5 shows a control mechanism relating toa vertical motion of the table rollers disposed in such equipment.

In FIG. 4 mentioned above, since the preceding metal block 1 and thesucceeding metal block 2 are joined with each other while they areconveyed, the metal blocks joining apparatus 4 first assumes a waitingposition on the upstream side (left side in FIG.4) of the conveying linefor the metal blocks. And, when the rear end portion of the precedingmetal block 1 and the fore end portion of the succeeding metal block 2reach to the joining apparatus 4, both metal blocks 1, 2 are clamped bypinch rolls P1, P2 disposed on the joining apparatus 4 while the joiningapparatus 4 runs at the same speed as the conveying speed of the metalblocks, and the rear end portion of the preceding metal block 1 and thefore end portion of the succeeding metal block 2 are heated and presseduntil the joining apparatus 4 reaches a predetermined position on thedownstream side of the line to complete the joining. On this occasion,the control unit 5 shown in FIG. 5 detects the position of the joiningapparatus 4 to operate driving cylinders 7 a-7 g through anelectromagnetic valve 6, respectively, to cause vertical motion of therespective movable table rollers 8 a-8 g for preventing them fromcolliding against the joining apparatus 4. In the equipment constructedas above, there is required a control by which the table rollerspositioned in front of the joining apparatus 4 are descended when thejoining apparatus 4 reaches thereto and the table rollers are ascendedimmediately after the joining apparatus 4 has passed therethrough.However, there is a problem relating the accuracy and reliability of theelectromagnetic valve 6 for performing the control and the verticalmotions of the table rollers, so that the joining apparatus 4 and thetable rollers 8 a-8 g may collide against each other. Also, inconnection with the driving cylinders 7 a-7 g for causing the verticalmotion of the table rollers 8 a-8 g, it has been recognizeddisadvantageous that the hydraulic apparatus has to be large in scaledue to a requirement for substantial flow rate of operating oil, andsuch apparatus has to be continuously operated thereby giving rise tosubstantial increase in the power loss and the running cost.

DISCLOSURE OF THE INVENTION

It is an object to provide a novel method for dissolving all of theconventional various problems in connection with implementation of acontinuous hot rolling, and various apparatuses which are used directlyfor carrying out said method.

The various problems described above as the tasks of the invention canbe advantageously attained by the constituent features described below.

Specifically, the invention provides a continuous hot rolling methodcomprising the steps of cutting a rear end portion of a preceding metalblock and a fore end portion of a succeeding metal block, respectively,heating and pressing the metal blocks to each other and thereby joiningthem with each other, and subsequently performing a finish rolling,wherein the method further comprises the step of restraining a region ofeach of the metal blocks extending from a clamping position to the endportion thereof for preventing a level change of the metal blocks uponheating and pressing the metal blocks (the first invention)

The invention further provides a continuous hot rolling methodcomprising the steps of cutting a rear end portion of a preceding metalblock and a fore end portion of a succeeding metal block, respectively,heating and pressing the metal blocks to each other thereby joining themwith each other, and subsequently performing a finish rolling, whereinthe method further comprises the step of restraining a region of each ofthe metal blocks passed by a magnetic flux and extending from a clampingposition to the end portion thereof, by means of a plurality of holdingmembers, for preventing a level change of the metal blocks upon heatingand pressing the metal blocks by an induction heating coil, said holdingmembers being arranged spaced apart from each other on surfaces of themetal blocks and having a width which is not greater than five times ofa penetration depth of an induced current by the heating coil (thesecond invention).

The invention further provides a continuous hot rolling methodcomprising cutting a rear end portion of a preceding metal block and afore end portion of a succeeding metal block, respectively, heating andpressing the metal blocks to each other and thereby joining them witheach other, and subsequently performing a finish rolling, wherein themethod further comprises the step of arranging a plurality of holdingmembers on a magnetic flux passing region of each of the metal blocksextending from a clamping position to the end portion thereof, forpreventing a level change of the metal blocks upon heating and pressingthe metal blocks by an induction heating coil, the holding members beingarranged spaced apart from each other on surfaces of the metal blocksand each having a width which is not greater than five times of apenetration depth of an induced current by the heating coil, therebyrestraining the metal blocks while maintaining an insulating statebetween the holding members and the metal blocks (the third invention).In this instance, it is preferable to perform the joining while blowingat least one of non-oxidizing gas and reducing gas onto a to-be-joinedface and a joined portion of the metal block.

The invention further provides a continuous hot rolling methodcomprising cutting a rear end portion of a preceding metal block and afore end portion of a succeeding metal block, respectively, heating andpressing the metal blocks to each other and thereby joining them witheach other, and subsequently performing a finish rolling, wherein themethod further comprises the step, upon joining the metal blocks by amovable joining apparatus, of escaping downwardly those table rollersfor conveying the respective metal blocks, which are situated in aregion below the movable joining apparatus, and returning the tablerollers to an initial level in a conveying region of the respectivemetal blocks (the fourth invention).

The invention further provides a continuous hot rolling methodcomprising cutting a rear end portion of a preceding metal block and afore end portion of a succeeding metal block, respectively, heating andpressing the metal blocks to each other and thereby joining them witheach other, and subsequently performing a finish rolling, wherein themethod further comprises the step of shaving off a poor joined portionfrom a surface of a base plate by a predetermined depth, upon removal ofthe poor joined portion of the metal blocks formed by pressing (thefifth invention). In this instance, it is preferable to control arotating cutter upon shaving off the poor joined portion, such that acircumferential speed thereof is 50-120 m/s.

The invention further provides a continuous hot rolling methodcomprising cutting a rear end portion of a preceding metal block and afore end portion of a succeeding metal block, respectively, heating andpressing the metal blocks to each other and thereby joining them witheach other, and subsequently performing a finish rolling, wherein themethod further comprises the step of cooling the joined portion afterjoining the metal blocks and before and/or after removing the poorjoined portion (the sixth invention).

The invention further provides a metal block joining apparatus in acontinuous hot rolling, which comprises heating means for heating themetal blocks to an elevated temperature, clamps having seizing portionswhich protrude toward the end portion of the metal block for clamping apreceding metal block and a succeeding metal block one above the other,and pressing means for moving and pressing at least one of the precedingmetal block and the succeeding metal block toward the other of the metalblocks (the seventh invention).

The invention further provides a metal block joining apparatus in acontinuous hot rolling, which comprises induction heating coil forheating the metal blocks to an elevated temperature, clamps for clampingand restraining a preceding metal block and a succeeding metal block oneabove the other, and pressing means for moving and pressing at least oneof the preceding metal block and the succeeding metal block toward theother of the metal blocks, each of the clamps having a notch portionnotched in a comb-like manner at regular intervals along a widthwisedirection of the metal block in a magnet flux region of a seizingportion which protrudes form a clamping and supporting portion of themetal block toward an end portion thereof (the eighth invention).

The invention further provides a metal block joining apparatus in acontinuous hot rolling, which comprises induction heating coils forheating the metal blocks to an elevated temperature, clamps for clampingand restraining a preceding metal block and a succeeding metal block oneabove the other, and pressing means for moving and pressing at least oneof the preceding metal block and the succeeding metal block toward theother of the metal block, at least one of the clamps having a notchportion notched in comb-like manners at regular intervals in a widthwisedirection of the metal block, and an insulation material bridged betweenthe metal blocks in a region over both of the metal blocks (the ninthinvention). In this instance, it is preferable to provide the clamp witha nozzle for blowing at least one kind of an non-oxidizing gas and areducing gas onto a to-be-joined face and a joined portion of the metalblocks.

The invention further provides a metal block joining apparatus in acontinuous hot rolling, which comprises heating means for metal blocks,clamps for clamping and restraining a preceding metal block and asucceeding metal block one above the other to thereby align levels ofthe metal blocks, and pressing means for moving and pressing at leastone of the preceding metal block and the succeeding metal block towardthe other of the metal blocks, moving means for moving each of saidmeans between an on-line position and an off-line position, andvertically movable table rollers for supporting the metal block at aregion where each of the means by the moving means have been moved tothe off-line position (the tenth invention).

The invention further provides a metal block conveying table rollerconveyor in a continuous hot rolling, which comprises a plurality oftable rollers for supporting the metal blocks at a plurality ofpositions along a longitudinal direction thereof, cylinders arrangedbelow and supporting the respective table rollers, and a hydrauliccircuit including a hydraulic pipe which communicates cylinder headswith each other, for maintaining an inner pressure of each of thecylinder heads at a constant pressure (the eleventh invention).

According to the invention, a region of the metal blocks extending froma position fixed by the clamps to the end portion thereof is restrainedfor preventing the end portion from deformation upon heating of themetal blocks to an elevated temperature, and thereby restricting avertical movement thereof. It is thus possible to avoid joining of themetal blocks which have been dislocated relative to each other, andprevent occurrence of bucklings (the first to third inventions and theseventh to ninth inventions).

According to the invention, furthermore, the clamps, the heating meansand the pressing means constituting the joining apparatus areindividually movable so that it is possible to decrease the thermal loadapplied to such means and extend the life of the apparatus (the tenthinvention).

According to the invention, furthermore, the table rollers for conveyingthe metal blocks are forced to escape to a position below the joiningapparatus upon arrival thereof, and to return to the metal blocksconveying region immediately after passage of the joining apparatus.Therefore, a complicated control is not required in connection with thevertical motion of the table rollers for positively preventing collisionof the table rollers against the joining apparatus, and it is possibleto simplify the apparatus (the fourth and eleventh inventions).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a state in which a preceding metal block and asucceeding metal block are heated to an elevated temperature by aninduction heating coil.

FIG. 2 is a view showing a state in which the preceding metal block andthe succeeding metal block are joined.

FIG. 3 is a view showing a state in which the joined metal blocks arebroken during the hot rolling.

FIG. 4 is a view explaining the structure of a conventional table rollerconveyor for conveying the metal blocks.

FIG. 5 is a view showing a mechanism for controlling the vertical motionof the table rollers shown in FIG. 4.

FIG. 6 is a view explaining the structure of the metal blocks joiningapparatus.

FIG. 7 is a sectional view taken along the line II—II of FIG. 6.

FIG. 8 is a view showing the structure of the metal blocks joiningapparatus.

FIG. 9 is a sectional view taken along the line II—II of FIG. 8.

FIG. 10 is a view showing a state in which the metal blocks are heatedwhen they are joined to each other.

FIGS. 11(a) and 11(b) are views showing states in which the metal blocksare heated when they are joined to each other.

FIG. 11(c) is a graph of current density.

FIG. 12 is a view showing the structure of the metal blocks joiningapparatus.

FIG. 13 is a view showing the entire structure of the apparatus shown inFIG. 12.

FIG. 14 is a view showing a state in which the joining apparatus isarranged in line with the continuous hot rolling equipment.

FIGS. 15(a) and 15(b) are views showing states in which the metal blocksare joined to each other.

FIG. 16 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 17 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 18 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 19 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 20 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 21 is a view showing the structure of the joining apparatusaccording to another embodiment.

FIG. 22 is a view showing the structure of the joining apparatus inwhich t he clamps, pressing means and heating means are individuallymovable.

FIG. 23 is a sectional view taken along the line II—II of FIG. 22.

FIG. 24 is a sectional view taken along the line II—II of FIG. 22.

FIG. 25 is a view showing one embodiment of the continuous hot rollingequipment provided with the joining apparatuses shown in FIG. 22 to FIG.24.

FIG. 26 is a view showing one example of use of the joining apparatusshown in FIG. 22.

FIG. 27 is a view explaining the structure of the table roller conveyorfor conveying the metal blocks.

FIG. 28 is a sectional view taken along the line II—II of FIG. 27.

FIG. 29 is a view showing another embodiment of the table rollerconveyor shown in FIG. 27.

FIG. 30 is a sectional view taken along the line II—II of FIG. 29.

FIG. 31 is a view explaining a state in which the table roller conveyorshown in FIG. 29 is operated.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be explained in detail hereinafter with reference tothe drawings.

FIG. 6 shows the structure of the metal blocks joining apparatus, andFIG. 7 shows the sectional view taken along the line II—II of FIG. 6.

In FIG. 6 and FIG. 7, reference numeral 9 denotes an induction heatingcoil for heating an end portion of the metal block to an elevatedtemperature, which is arranged in such a manner that a preceding metalblock 1 and a succeeding metal block 2 are passed through the centerspace portion thereof. Reference numeral 10 denotes an outlet framewhich is arranged on the outlet side of the induction heating coil 9 insuch a manner that the preceding metal block 1 and the succeeding metalblock 2 can be passed through the center space portion thereof.Reference numeral 11 denotes an inlet frame which is provided withhydraulic cylinders 12 as means for pressing the metal blocks, and whichis arranged on the inlet side of the heating means 9 in such a mannerthat the preceding metal block 1 and the succeeding metal block 2 can bepassed through a center space portion thereof.

Hydraulic cylinders 13 are disposed on the upper portion and the lowerportion of each of the inlet and outlet frames 10, 11 such that theirrespective rod portions extend therethrough. Each hydraulic cylinder 13is provided at the leading end of the rod portion thereof with a clamp14 for clamping an end portion of the metal block from above and belowto thereby fixedly hold it.

Reference numeral 15 denotes a seizing portion for restraining a regionextending from a position of the clamp 14 to the end portion of themetal block in order to prevent a level change, in the verticaldirection, of the metal blocks upon pressing the metal blocks. Theseizing portion 15 has a notch portion 15 a notched in a comb-likemanner at regular intervals along a widthwise direction of the metalblock, and is mounted on each of the upper and lower clamps 14 which areattached to the leading ends of the rod portions of the hydrauliccylinders 13.

The preceding metal block 1 and the succeeding metal block 2 arearranged opposite to each other leaving a minute clearance therebetween,and pressed against each other with the clamp 14 and the seizing portion15 by means of the hydraulic cylinders 12 so that they are restrainedfrom above and, below. In this state, the preceding metal block 1 andthe succeeding metal block 2 are applied with an alternate magneticfield by the induction heating coil 9 and thereby heated to an elevatedtemperature, and both of the metal blocks are pressed by operating thehydraulic cylinders 12, so that the metal blocks can be joinedpositively and in a short time without causing vertical dislocation andbuckling of the metal blocks.

In this instance, a high frequency current is supplied to the inductionheating coil 9 such that an alternating magnetic field is applied to themetal blocks to penetrate therethrough in the thickness direction and aninduced current “e” is caused to flow on a plane of the metal blockswhereby they are heated to an elevated temperature in a short time.

The current density of the induced current “e” generated on suchoccasion has a distribution with reference to the end portion of theplate, which is represented by the following equation.

i(x)=i_(O) exp(−x/δ)

x: the distance from the end portion of the plate

δ: the penetrating depth of the induced current

Here, δ is defined by$\frac{1}{2\pi}\sqrt{\left( {\rho \times 10^{7}} \right)/\left( {\mu \cdot f} \right)}$

f: frequency of the alternating magnetic field (Hz)

ρ: specific resistance (Ω·m)

μ: relative permeability (−)

When thus constructed joining apparatus is provided with a seizingportion 16 shown in FIG. 8 and FIG. 9 for restraining the metal blockover the whole region in the widthwise direction thereof, instead of theseizing portion 15 of the clamp 14, a similar effect can be achieved.However, when the induction coil is used particularly as the heatingmeans in the apparatus including such a seizing portion 16, the inducedcurrent “e” is caused to flow on the seizing portion 16 as shown in FIG.10, so that the seizing portion 16 is heated to an elevated temperaturetogether with the metal blocks 1, 2, thereby lowering the heatingefficiency and causing the seizing portion 16 to be melted and welded tothe metal blocks.

Therefore, in the joining apparatus provided with the clamps 14 havingthe seizing portion 16 shown in FIG. 8 and FIG. 9 mentioned above, it ispreferable to incorporate a heating means using gas, torch, laser andthe like is.

Upon heating the metal blocks, an induced current is caused to flow inthe seizing portion 15 constructed as shown in FIG. 6 and FIG. 7mentioned above. By forming notch portions 15 a in a comb-like manner atregular intervals along the widthwise direction of the metal blocks, theinduced current “e” in the comb teeth 15 b becomes a circulatingcurrent, as shown in FIGS. 11a and 11 b. Apparent induced currents e₁and e₂ shown by dotted lines in FIG. 11c which illustrates a major partof the seizing portion 15, are opposite in direction to each other andinteract to cancel each other. Thus, as FIG. 11c shows, an actualcurrent density is decreased as shown by the solid line, and generationof Joule's heat is reduced and the magnitude of heating becomes small.Therefore, the heating efficiency upon joining can be advantageouslyimproved. In this connection, it should be noted that the inducedcurrent flows on the end surface of the metal block due to the skineffect. Moreover, melting of the seizing portion 15 and welding to theplate member are prevented.

It is desirable to make the width of each of the comb teeth 15 b in theseizing portion 15 as the holding member within two times (but not zero)of the penetrating depth of the induced current, from the viewpoint ofloss upon heating, though they are advantageously greater in width fromthe viewpoint of strength and rigidity. The width of the comb tooth 15 bcan be made up to about five times of the penetration depth, byperforming cooling and the like. Of course, according to the invention,cooling may be performed in combination with the comb teeth whose widthis not greater than two times of the penetrating depth.

FIG. 12 shows another embodiment of the joining apparatus according tothe invention, in which one set of the seizing portions 15 of the clamps14 is made to have such a length as to extend over the preceding metalblock 1 and the succeeding metal block 2, and provided with aninsulation material 17 in that region which extends over both of themetal blocks at the seizing portion 15, that is, between the metalblocks.

Hydraulic cylinders or the like driving means (not shown) are connectedto the clamps 14 for clamping the preceding metal block 1 and thesucceeding metal block 2 one above the other and thereby restrainingthem. The driving means are vertically movable toward and away from eachother. The seizing portions 15 may be constituted by SUS304, titanium,tungsten and the like, and are connected to the clamps 14 for preventingthe end portions of the metal blocks from being joined to each otherwith a vertical dislocation as the metal blocks are pressed to eachother, and also for preventing occurrence of bucklings. Each of theseizing portions is provided with a notch portion 15 a that is notchedin a comb-like manner at regular intervals along the widthwise directionof the metal block, and also with an insulating material 17. Since theend portions of the metal blocks are heated to high temperature and maybe partly melted, the insulating material comprises a ceramic and thelike material having sufficient heat resistance, heat impact resistanceand high-temperature strength.

The entire construction of the joining apparatus shown in theabove-mentioned FIG. 12 is illustrated in FIG. 13, and a state in whichsaid apparatus is arranged in line with the continuous hot rollingequipment is illustrated in FIG. 14.

In FIG. 13 and FIG. 14, reference symbol “r” denotes a rough rollingmill, “c” is a Crop shear for working the end portion of the metal blockin a desired shape, “m” is a group of finish rolling mills, and “f” is amovable frame constituting the joining apparatus. There may be arrangeda winding/unwinding apparatus (not shown) for ensuring a time adjustmentof the joining work and the rolling work of the metal blocks, betweenthe rough rolling mill “r” and the Crop shear “c” in FIG. 14.

In order to form a butt-joint between the preceding metal block 1 andthe succeeding metal block 2 at their respective end portions by usingthe apparatus shown in FIG. 12, the preceding metal block 1 isrestrained and positioned by the clamps 14 as shown in FIG. 15(a), andthe succeeding metal block 2 is subsequently restrained and positionedby the other clamps 14 such that a gap “g” is formed between thepreceding metal block 1 and the succeeding metal block 2. The metalblocks are then heated to an elevated temperature by the inductionheating coil 9. The clamps 14 of which the seizing portions 15 extendover both of the metal blocks are moved as shown in FIG. 15(b), with themetal blocks caused to slide at the insulation portion, to butt thesucceeding metal block 2 against the end surface of the preceding metalblock 1. In this instance, the preceding metal block 1 may be movedtoward the succeeding metal block 2.

The apparatus constituted as shown in the above-mentioned FIG. 12 hasbeen illustrated as an embodiment in which the seizing portions 15 areextended over the preceding metal block 1 and the succeeding metal block2 together with the insulating material 17. However, according to theinvention, the seizing portions 15 can be arranged on the respectiveclamps 14 of the preceding metal block 1 and the succeeding metal block2, as shown in FIG. 16. In this instance also, it is possible to preventdislocation, in the vertical direction, of the metal blocks when theyare pressed to each other.

However, such a construction may have disadvantageous facet inpreventing the vertical dislocation or bucklings of the metal blocks forensuring a positive joining. Thus, it is preferable to arrange theseizing portions 15 so as to extend over both of the preceding metalblock 1 and the succeeding metal block 2.

This is due to the following reasons. It is important for the buttedfaces of the preceding metal block 1 and the succeeding metal face 2 tobe aligned with the center of the induction heating coil 9, i.e., thedimensional center of the metal block in the longitudinal directionthereof, though certain dislocation is inevitable upon positioning.Also, when carrying out the heating between the preceding metal block 1and the succeeding metal block 2 to an elevated temperature, there maybe instances wherein the metal blocks are intentionally dislocated toperform an asymmetrical heating. In this case, if both of the metalblocks are pressed to each other as shown in FIG. 16, the end portionsof the metal blocks exhibit an enhanced tendency to be dislocated in avertical direction, and the dislocation amount increases when the metalblocks themselves are curved. Accordingly, it is most appropriate toprovide one set of the clamps for restraining the metal blocks, with theseizing portion 15 having the insulation material 17 so that, uponpressing the preceding metal block 1 and the succeeding metal block 2,the level of both of the metal blocks are aligned with each other.

The reason why the insulating material 17 is disposed on the seizingportion 15 is that, when the seizing portion 15 is disposed to extendover both of the metal blocks, the metal blocks are brought into contactwith the seizing portion 15 so that an induced current flows betweenboth of the metal blocks through the seizing portion 15, thereby makingit difficult to effectively heat the end portions of the metal blocks toan elevated temperature.

As shown in the above-mentioned FIG. 16, also when the seizing portions15 are disposed on the respective metal blocks, the insulating material17 is preferably arranged between the seizing portion 15 and the metalblocks so as eliminate the influence of the induced current to the metalblocks.

In FIG. 12 mentioned above, there is shown one embodiment in which theseizing portion 15 disposed on each of the preceding metal block 1 andthe succeeding metal block 2 includes a notch portion 15 a. However,when one of the seizing portions 15 is shifted from the position of theinduction heating coil 9, or when the induced current due to theapplication of the alternating magnetic field by the induction heatingcoil 9 does not give rise to particular problems, it is not necessaryfor the other of the seizing portion 15 to have the notch portion 5 a.

Moreover, when the magnetic flux due to the induction heading coil 9 isapplied not only to the seizing portions 15 but also to the clamps 14,the notch portions 5 a are preferably extended and formed to reach tothe clamps 14.

FIG. 17 shows one embodiment in which a cooling water passage “p” isdisposed inside the seizing portion 15 to realize a water cooling typestructure, and a nozzle N is disposed through the insulating material 17for ejecting a non-oxidizing or reducing gas or a cooing water onto theto-be-joined face of the metal blocks.

When the temperature of the seizing portion 15 is inevitably increasedupon heating the metal blocks, the increase can be suppressed bycirculating the cooling water inside the seizing portion 15. Moreover,upon butt-joining of the metal blocks, the non-oxidizing gas or reducinggas is ejected onto the to-be-joined face by performing a changeoverfrom the nozzle N to valves b₁-b₃ so that the ejected portion isprevented from oxidization, thereby making it possible to realize ajoined portion with high strength. The strength can be further improvedby changing over the valves b₁-b₃ after completion of the joining, so asto eject the cooling water onto the joined portion and lower thetemperature of the ejected portion. It should be noted that the joinedportion may be broken upon variation of tension or the like, when thetemperature of the joined portion is 1,450° C. or more. As regards thecooling of the joined portion, it is preferable to effect the cooling ata flow rate of 100-400 t/h (one side face). There may be used a nozzle Nof 1-2 mm in diameter, or of a slit type which is about 1 mm in gap and5-10 mm in width.

In FIG. 17, the cooling water and the like is ejected through theseizing portion 15 and the insulating material 17. However, as shown inFIG. 18, the nozzle N may be directly attached to the insulatingmaterial 17 through the notch portion 15 a.

When the seizing portion 15 and the insulating material 17 are disposedon each of the metal blocks as shown in FIG. 16, the nozzles N may bedisposed onto the leading ends of the seizing portions 15, respectively,as shown in FIG. 19.

FIG. 20 shows one embodiment of the metal blocks joining apparatusprovided with a seal box 18 which surrounds a rear end portion of thepreceding metal block 1 and a fore end portion of the succeeding metalblock 2, for maintaining the surrounded portions at an atmosphere of thenon-oxidizing gas or reducing gas. The seal box has anexpansion/contraction function so as to prevent interference with theclamps 14 as they are moved in a vertical direction.

By introducing the non-oxidizing gas such as N₂ gas and the like intothe seal box 18, the inside of the seal box 18 can be maintained at anatmosphere which is suitable for joining. In this case, while thearrangement for exhausting the introduced gas is not shown in thedrawings, a gas suction hole may be disposed in another side of the sealbox 18 to discharge the gas therefrom.

The metal blocks can be advantageously joined to each other by using theseal box 18 shown in FIG. 20, particularly when the object is a metalwhich cannot be easily joined in the atmosphere, such as stainless steelincluding Cr, high carbon special steel having a low meltingtemperature, high manganese steel and the like.

The gas to be introduced into the seal box may be N₂ gas, Ar gas and thelike, or may be a non-oxidizing gas such as H₂ gas, CO gas and the like.When such gas is used, the flow rate should be about 1-10 Nm³/min.

When the metal block is carbon steel, for example, the oxide generatedupon heating is ferrous oxide (FeO) and the melting point thereof isabout 1,370° C. Even when it is mixed, for example, with MnO and thelike, the melting temperature is in the vicinity of said temperature. Itshould be noted that the melting temperature of the metal changesdepending upon the amount of carbon content. With respect to a steelhaving a solidus curve higher than the melting temperature of FeO, whenthe temperature is between the solidus curve and the melting point ofFeO, the molten oxide can be discharged from an interface between themetal blocks when deforming the metal upon pressing the metal blocks.

Incidentally, as for a steel having a carbon content of about 0.70%, asolidus curve temperature where a dissolution is initiated substantiallyagrees with the melting point of Fe oxide, so that the oxide on theinterface generated upon heating the metal block is not melted and maybe left on the interface of the joined portion, making it difficult toobtain a satisfactory joined portion.

Moreover, since the oxide generated on the stainless steel is Cr oxidewhich is very strong and has a melting point much higher than that ofthe metal, when the metal blocks are joined by being heated in theatmosphere, the oxide is left on the interface as described above and itis thus very difficult to obtain a satisfactory joined portion.

These problems can be advantageously mitigated by using the seal box 18such as that shown in FIG. 20.

Investigation has been carried out to ascertain the forming state ofoxide with respect to metal blocks comprised, respectively, of anextremely low carbon steel and a stainless steel each cut by a Cropshear, whose end portions were maintained at 950-1,000° C. in theatmosphere for 15 seconds. As a result, it has been found that an oxidelayer of several μm in thickness was formed in case of the extremely lowcarbon steel, though formation of oxide was hardly recognized in case ofthe stainless steel. Incidentally, when these steels are further heatedup to 1,400° C., oxide layer of about 60-70 μm in thickness is formed incase of the extremely low carbon steel and also the oxide layer ofseveral μm is formed in case of the stainless steel. However, formationof such oxide layer can be prevented by establishing a non-oxidizing orreducing atmosphere only during the heating.

Moreover, in order to prevent oxidization of the to-be-joined faceduring the heating, it is preferable to adjust the atmosphere such thatthe oxygen concentration becomes 1% or less in case of the carbon steel,and about 0.1% in case of the stainless steel.

FIG. 21 shows a modified embodiment of the apparatus in FIG. 12mentioned above. The embodiment shown in FIG. 21 has a construction inwhich the upper clamp 14 for restraining the metal blocks is verticallymovable, and the seizing portion 15 disposed on one of the lower clamps14 is adapted to slide on the sliding plate “t” disposed on the other ofthe lower clamps 14.

Such an arrangement of the apparatus ensures that the level of the lowerclamps 14 is maintained constant and thus serves to advantageouslyimprove the positioning accuracy in joining the metal blocks and thestrength of the clamps.

By constructing the metal blocks joining apparatus as described above,the metal blocks can be effectively heated to an elevated temperature,and the vertical dislocation or the like caused during the pressing ofthe metal block can be minimized.

Next, explanation will be made of the joining apparatus having aconstruction in which the clamps and the pressing means are adapted tomove in the widthwise direction of the metal block independently of theheating means for lower the thermal load, etc., to which the clamps andthe pressing means are subjected.

The construction is shown in FIG., 22 to FIG. 24.

In the drawings, reference numeral 19 denotes a carriage which ismovable on a rail L disposed along a conveying line of the metal blocks.The induction heating coil 9 as the heating means is shown as, forexample, a C-shape core for sandwiching the metal blocks from above andbelow, and is provided with a coil wound around the core and an electricsource (not shown). The induction heating coil 9 is suspended andsupported on a frame 20 (moving means) through wheels 20 a, and theframe 20 extends along the widthwise direction of the metal block in thecarriage 19, such that the induction coil 9 is adapted to moveindependently in the widthwise direction of the metal block in thecarriage 19 as shown in FIG. 23. The moving means in the carriage 19 ofthe induction heating coil 9 may be of a slide type.

Also, reference numeral 21 denotes a frame (moving means) of an integraltype including upper and lower portions, which is movable in thewidthwise direction independently of the induction heating coil 9. Theframe 21 comprises clamps 14 for adjusting the levels of the metalblocks, and a hydraulic cylinder (pressing means) 12 for moving andpressing at least one of the preceding metal block and the succeedingmetal block toward each other when they are press-sandwiched andsupported by the clamps 14. As a moving mechanism disposed in thecarriage 19 of the frame 21 for moving the clamps 14 and the hydrauliccylinders 12, there may be provided a mechanism comprising a rail L₁ andwheels 21 a adopted to the rail L₁, though a moving mechanism such as aroller type mechanism, a slide type mechanism or the like may also beapplied. It should be noted that the moving mechanism is not shown inFIG. 23 and FIG. 24. Further, reference numeral 22 denotes table rollersfor conveying the metal blocks, which are vertically movable accordingto the movement of the carriage 19 so as to achieve a function ofpreventing collision against the carriage 1.

In thus constructed metal blocks joining apparatus, the joining of thepreceding metal block 1 and the succeeding metal block 2 is carried out,as shown in FIG. 22 and FIG. 23, by restraining the end portions of themetal blocks by the clamps 14 moved in the carriage 19 into the in-lineposition, heating each end portion to an elevated temperature by theinduction heating coil 9 which has been moved in the carriage 19, andpressing at least one of the preceding metal block 1 and the succeedingmetal block 2 toward each other by the hydraulic cylinders 12 which havebeen moved together with the clamp 14 into the in-line position tothereby butt the respective metal blocks to each other.

After completion of one cycle of continuous rolling wherein 15 metalblocks, for example, are joined and then transferred to a group of hotfinish rolling mills, as shown in FIG. 24, the induction heating coil 9is moved along the frame 20 and a frame 21 provided with the clamps 14and the hydraulic cylinders 12 is moved along the rail L₁ from theconveying line P of the metal blocks so that the induction heating coil9 assumes a waiting position until arrival of the next metal blocks.Incidentally, when the clamps 14 and the hydraulic cylinder 12 aresupposed to be moved off the line in the course of conveying the metalblocks, it is preferable for the frame 21 to be formed into the sameC-like shape as the induction heating coil 9, or as a frame which can beopened vertically.

FIG. 25 shows one embodiment of the continuous hot rolling equipment ofthe metal blocks, in which the joining apparatus constructed as abovecan be suitably arranged.

The joining apparatus is arranged between the cutting apparatus 23 onthe outlet side of the rough rolling mill “r” for finishing the endportion of the metal block in a predetermined plain shape prior to thejoining of the metal blocks, and a group of hot finish rolling mills 24.In such a type of continuous hot rolling equipment, there may beinstances in which a winding/unwinding apparatus is arranged on theoutlet side of the rough rolling mill “r” in order to adjust thetreating amount in the rough rolling and finish rolling steps.

FIG. 26 shows a conveying state of the metal blocks in the carriage 19,with the induction heating coil 9, the clamps 14 and the hydrauliccylinder 12 moved off the line.

Usually, the metal blocks are conveyed in the carriage 19 while beingslid. However, in the apparatus according to the invention, the insideof the carriage 19 can be made empty, so that vertically movable supportrollers 25 are additionally disposed therein so as to support the metalblocks. The support rollers may be of a type in which the rollers areattached to the carriage 19 and caused to move upwards only when theyare used, or of a type in which the rollers are arranged below thecarriage 19 for avoiding collision with the carriage 19 as it moves, andare caused to move upwards only when they are used. Such an arrangementserves to advantageously prevent formation of scratches due to scalesdeposited in the carriage 19.

As described above, in the joining apparatus constructed as shown inFIG. 22 to FIG. 24, the clamp and the pressing means subjected to asubstantial thermal load are moved off the line when the metal blocksneed not be joined, so that their life time can be extended and itbecomes possible to prevent formation of scratches due to the depositionof scales. Further, when maintenance is required for some troubles, theoperation can be continued without stopping the operation of the line,by substituting another frame provided with the clamps and the pressingmeans. It is thus possible to perform a hot rolling with a highproductivity, requiring a relatively small space since the entirejoining apparatus need not be moved.

A table roller device for conveying the metal blocks will be describedbelow.

The construction is shown in FIG. 27 and FIG. 28, of which the latter isa sectional view taken along the line II—II of FIG. 27.

In the drawings, a table roller device for conveying the metal blockscomprises a plurality of rollers 26 for supporting the metal blocks at aplurality of positions along the longitudinal direction of the metalblocks. For each table roller, both ends thereof are rotatably supportedon a set or pair of table roller supporting members 27. A rack 28 isattached on a side face of each table roller supporting member 27 andmounted movably along a vertical guide frame 29. Reference numeral 30denotes cylinders (i.e., balance cylinders) connected at one end to theguide frame 29 and at another end to the table roller supporting member27. Reference numeral 31 denotes guide rollers, which are held rotatablyon the upper portion of the guide frame 29.

Reference numeral 32 denotes pinions connected to a mechanical tyingshaft 33 and supported rotatably on the upper portion of the guide frame29.

Reference numeral 34 denotes a joining apparatus movable along the railL₂, which is provided with a frame 35, wheels 36, boat-like guide rails37 disposed on both sides of a lower face of the frame 35 and having aninlet portion and an outlet portion both inclined toward a centerportion thereof, clamps 38 for sandwiching the metal blocks from aboveand below to restrain them, and a heating means 39.

Reference numeral 40 denotes a hydraulic pipe connected to head sides ofthe respective cylinders 30 and provided with an accumulator 41 and ashut valve 42 on the way up to the rolling apparatus (not shown).

Reference numeral 43 denotes fixed table rollers which are not allowedto undergo a vertical motion and which are disposed on the inlet andoutlet sides of the metal blocks joining apparatus 34 and used forconveying the metal blocks.

In thus constructed table roller device for conveying the metal blocks,a predetermined pressure is applied to the inlet side of each cylinder30 and the accumulator 41, and the pressure is maintained by closing theshut valve 42.

The metal blocks are conveyed through the table roller 43 with thejoining apparatus 34 shifted toward a side in which the succeeding metalblock is conveyed, and the joining apparatus 34 is then moved at thesame speed as the metal blocks when they reach the joining apparatus 34.The preceding metal block 1 and the succeeding metal block 2 are thenrestrained by the clamps 38, respectively, and then heated to anelevated temperature by the heating means 39 until the metal blocksreach a stop end of the joining apparatus 34, where the joining of themetal blocks is finished.

When the joining apparatus 34 moves, the guide rail 37 moves togetherwith the joining apparatus 34. On this occasion, the guide rollers 31and the table rollers 26 situated between the inclined inlet portion andthe center portion of the guide rail 37 are caused to move upwardsaccording to the passage of the joining apparatus 34. Conversely, theguide rollers 31 and the table rollers 26 situated between the inclinedoutlet portion and the center portion of the guide rail 37 are urged bythe inclined outlet portion and the center portion of the guide rail 37due to the arrival of the joining apparatus 34 and thereby caused tomove downwards. Accordingly, the metal blocks are prevented fromcolliding against the frame 35 constituting the joining apparatus 34.

The metal blocks conveying table roller device according to theinvention is so constructed that the head sides of the respectivecylinders 30 for supporting the table rollers 26 together with thesupporting member 27 from below are connected to each other by thehydraulic pipe 40, forming a hydraulic circuit for maintaining thepressure in the respective head sides at a constant pressure. Thus, theoil inside the cylinder 30 associated with the table rollers 26 and thesupporting members 27 which have moved downwards is merely transferredto the cylinder 30 associated with the table rollers 26 and thesupporting members 27 which have moved upwards, thereby making itpossible to positively support the metal blocks while the table rollersare prevented from colliding against the joining apparatus 34. It isunnecessary to operate or control the valves for this purpose.

In the construction having the supporting members 27 for supporting thetable rollers 26 at the respective shaft ends thereof, by connecting theboth side portions of the supporting members through the mechanicaltying shaft 33, the table rollers 26 are always held horizontally evenwhen the guide rollers 31 are not guided on the guide rail 37, so thatthe metal blocks can be positively supported and conveyed.

As shown in FIG. 27 and FIG. 28 mentioned above, when, for example, theheating means, the pressing means and the clamps are taken out from thejoining apparatus 34 and only the frame 35 is arranged at the in-linewaiting position where the metal blocks are not joined, the metal blocksmay not be properly supported in the frame 35 by the table rollers 26.

In this case, as shown in FIG. 29 and FIG. 30 which is a sectional viewtaken along the line II—II in FIG. 29, a detachable shift guide rail 37a is disposed on, for example, a center portion of the guide rail 37 andthe shift guide rail 37 a is moved in a direction away from theconveying line as shown in FIG. 31 by a shifting cylinder disposed onthe frame 35, to thereby ensure a space through which the table rollers26 can be moved upwardly so as to face the conveying line.

In order to cause an upward movement of the table rollers 26 existing inthat area, the pressure of the hydraulic pipe 40 is once lowered and theshift guide rail 37 is moved in a direction away from the convener line.Then, by applying a pressure to the hydraulic pipe 40, the table rollers26 are moved upwardly via the cylinders 30 and table roller supportingmembers 27.

For performing the above-mentioned operations, the shut valve 42 ispreferably comprised of a three-way valve and the like, having thefunctions of opening, closing and pressure-releasing.

Moreover, FIG. 29 to FIG. 31 show an embodiment of the shift guide rail37 a having a length which is sufficient for causing an upward movementof only one of the table rollers 26. However, when the guide rails 37are long enough to allow an upward movement of a plurality of the tablerollers, it is enough to lengthen the shift guide rails 37 a by acorresponding amount.

In the metal blocks conveying table roller device constructed as above,the cylinders 30 supporting the table rollers 26 from below areequivalent in pressure with each other, and the sum of descendingdisplacements of the respective table rollers moved by butting the guiderail 37 with the guide rollers 31 is always constant. Thus, only bymaintaining a constant pressure in the hydraulic circuit including thecylinder 30, the hydraulic pipe 40, accumulator 41, and the shut valve42, the vertical motion can be performed without additional provision ofa hydraulic apparatus and the like having an electromagnetic valve forthe vertical motion, so that the power required for driving the guideroll can be saved.

Moreover, both ends of the table rollers 26 are connected through themechanical tying means and are thus always maintained at the same level.Thus, even when the guide rollers 31 turn out not to be guided on theguide rail 37, the table rollers 26 facing the conveying line can beheld horizontally due to an urging force in the head side of thecylinder 30, thereby allowing the metal blocks to be positivelysupported and conveyed.

INDUSTRIAL APPLICABILITY

According to the invention, the following advantageous effects can beachieved.

(1) Since the deformation of the fore end portion and the rear endportion of the metal blocks upon heating and pressing can be prevented,it is possible to prevent joining of the relatively dislocated metalblocks and occurrence of buckling. Accordingly, it is possible toprevent during the rolling a breakage of the plate due to suchdislocation (the first to third inventions).

Also, it is possible to achieve a proper joining by ejecting gas andwater to optimize the joining condition of the metal blocks, therebyallowing a continuous hot rolling to be performed with a highproductivity.

(2) The table rollers can be prevented from collision against the movingtype joining apparatus without performing a complicated control relatingto the vertical motion of the table rollers, so that the metal blockscan be conveyed stably (the forth invention).

(3) A smooth rolling can be performed over the entire length of themetal blocks including the connected portion (the fifth invention).

(4) The poor joined portion can be removed effectively. Further, thestrength of the connected portion of the metal blocks can be increasedso that the plate during transfer does not undergo a breakage even uponsignificant deviation in tension (the sixth invention).

(5) The end portions of the metal blocks are prevented from a verticaldislocation or buckling (the seventh to the ninth inventions). Also, theseizing portion of the clamps can be prevented from being welded ordeposited to the plate, and the heating efficiency can be improved (theeighth and the ninth inventions).

(6) Not only the induction heating coil but also the clamps and thepressing means can be moved properly to the outside of the line, so thatthe thermal load of the entire joining apparatus can be minimized andthe maintenance of the joining apparatus can be performed easily.Conventionally, the table rollers for conveying the metal blocks couldnot be arranged inside the carriage, so that a construction over whichthe metal blocks moves in a sliding manner could not be adopted. In thisinstance, it was impossible to prevent formation of scratches whenscales are deposited. According to the invention, however, formation ofscratches due to scales can be prevented, since the metal blocks can besupported by the guide rollers and the like in the carriage with theheating means, the clamps and the pressing means evacuated (the tenthinvention).

(7) Since the vertical movement of the table rollers is automaticallyand promptly performed according to the running state of the joiningapparatus, it is possible to avoid an accident wherein the joiningapparatus collides against the table rollers. Also, it is possible toavoid a situation wherein the metal blocks cannot be supported due to aslow upward motion of the table rollers after the passage of the joiningapparatus. Further, since the table roller device is of a balance type,the table rollers can be moved vertically by allowing the hydraulic oilof the cylinders for supporting the table rollers to flow just from oneto another in accordance with the movement of the joining apparatus. Tothis end, it is only necessary to pressurize the inside of the hydrauliccircuit at a constant pressure and a complicated control is not requiredto operate the hydraulic apparatus for vertically moving the tablerollers, making it possible to minimize the power consumption.Furthermore, the table rollers on both sides can be held at the samelevel even when the guide rollers do not contact with the guide rail, sothat the metal blocks can be positively supported and conveyed (theeleventh invention).

What is claimed is:
 1. A metal block conveying apparatus in a continuoushot rolling wherein a rear end portion of a preceding metal block and afore end portion of a succeeding metal block are heated and pressedagainst each other so that the preceding metal block and the succeedingmetal block are joined to each other by a movable joining apparatuswhile the metal blocks are conveyed along the conveying apparatustogether with the joining apparatus, said metal block conveyingapparatus comprising: a plurality of table rollers and guide rollers forsupporting the metal blocks at a plurality of positions along alongitudinal direction of the metal blocks; guide rails that are movablewith the joining apparatus and engaged with said guide rollers, saidguide rails each having a guide surface with a predetermined profile; aplurality of cylinders arranged below and supporting the respectiveguide rollers, said cylinders being operable to follow movement of therespective guide rollers vertically; upwards and downwards as the guiderollers are moved relative to, and along the guide surfaces of the guiderails; and a hydraulic circuit comprised of a hydraulic pipe whichcommunicates cylinder heads of the cylinders with each other, formaintaining an inner pressure of each of the cylinder heads at aconstant pressure.
 2. The metal block conveying apparatus according toclaim 1, wherein said hydraulic circuit is further comprised of anaccumulator.
 3. A continuous hot rolling mill comprising: a metal blockconveying apparatus for continuously conveying successive metal blocks;and a movable joining apparatus for joining a preceding metal block anda succeeding metal block to each other by heating and pressing a rearend portion of a preceding metal block and a fore end portion of asucceeding metal block against each other, while the metal blocks areconveyed along the conveying apparatus together with the joiningapparatus, said metal block conveying apparatus comprising; a pluralityof table rollers and guide rollers for supporting the metal blocks at aplurality of positions along a longitudinal direction of the metalblocks; guide rails that are movable with the joining apparatus andengaged with said guide rollers, said guide rails each having a guidesurface with a predetermined profile; a plurality of cylinders arrangedbelow and supporting the respective guide rollers, said cylinders beingoperable to follow movement of the respective guide rollers verticallyupwards and downwards as the guide rollers are moved relative to, andalong the guide surfaces of the guide rails; and a hydraulic circuitcomprised of a hydraulic pipe which communicates cylinder heads of thecylinders with each other, for maintaining an inner pressure of each ofthe cylinder heads at a constant pressure.
 4. The continuous hot rollingmill according to claim 3, wherein said hydraulic circuit of the metalblock conveying apparatus is further comprised of an accumulator.